Rhizoprionodon acutus


Milk shark RHA
Characteristic features:
Colour:

Dorsal surfaces bronze to greyish, fading to grey after death. Pectoral, pelvic, anal and lower caudal-fin tips and pectoral-fin posterior margins pale; upper lobe of caudal edged with black and with a dusky tip. Ventral surfaces white.

Size:

Maximum size up to 100 cm TL; birth size 31–39 cm TL.

Distribution:

Found in tropical waters of the eastern Atlantic and Indo–West Central Pacific Oceans.

Habitat:

Occurs throughout water column, but mainly near the bottom, over continental and insular shelves from the intertidal to at least 200 m depth.

Biology:

Feeds primarily on small bony fish, and also crustaceans and cephalopods. Populations appear to have increased in some areas where there have been declines in large inshore sharks (e.g. South Africa). Regional differences in some DNA sequences suggest this may represent a complex of species. Length at maturity is 70–81 cm TL and 68–72 cm TL for females and males respectively. Age at maturity is around 1.8 years for females and 1.1 years for males. Reproductive mode is viviparous with yolk-sac placenta; females give birth to 1–8 (usually 2–5) pups after a gestation period of about 12 months. Females have no reproductive seasonality and probably give birth each year. Maximum age of northeastern Australian populations reported for females and males as 8.1 and 4.5 years respectively.

Indonesian fisheries:

Commonly caught by inshore demersal gillnet fisheries. Utilised for its fins and meat, but of limited value due to its small size.

Similar species:

Rhizoprionodon oligolinx
Grey sharpnose shark

Rhizoprionodon oligolinx

Rhizoprionodon oligolinx differ in having short upper labial furrows (vs. long and prominent).

Rhizoprionodon taylori
Australian sharpnose shark

Rhizoprionodon taylori

Rhizoprionodon taylori differ in having short upper labial furrows (vs. long and prominent).

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